Anesth Analg 2003;97:601
© 2003 International Anesthesia Research Society
LETTERS TO THE EDITOR
Mechanisms of Postoperative Neurobehavioral Deficits and Stroke May Differ
Deborah J. Culley, MD, and
Gregory Crosby, MD
Department of Anesthesiology, Perioperative, and Pain Medicine, Brigham & Women’s Hospital, Harvard Medical School, Boston, MA
To the Editor:
We enjoyed the editorial by Butterworth and Hammon (1) on lidocaine protection against postcardiopulmonary bypass cognitive dysfunction. We disagree, however, with their assertion that it is a "reasonable assumption that strokes and neurobehavioral deficits result from similar brain injury mechanisms." There is now ample evidence that a substantial percentage of patients undergoing even routine general surgical procedures experience cognitive impairment for weeks or months thereafter (2,3). The etiology of this neurobehavioral impairment is unknown, but there is little reason to think it is due to subclinical structural neurologic injury, since, with the exception of cardiac, neurological, and a few orthopedic surgical procedures, stroke-promoting events such as emboli are unusual. Moreover, efforts to link worrisome systemic physiologic events associated with anesthesia such as hypotension and hypoxemia with postoperative cognitive dysfunction have been unsuccessful (2,3). Finally, although we do not expect the authors to be aware of soon-to-be-published data, we have laboratory evidence that isoflurane–nitrous oxide anesthesia impairs learning for several weeks in young and old rats (4,5), suggesting general anesthesia itself may affect neurochemical cascades mediating memory for longer than previously realized. Therefore, while stroke can produce cognitive impairment, there is almost certainly more to postoperative cognitive impairment than clinical or subclinical stroke.
References
- Butterworth J, Hammon JW. Lidocaine for neuroprotection: more evidence of efficacy. Anesth Analg 2002; 95: 1131–3.[Free Full Text]
- Moller JT, Cluitmans P, Rasmussen LS, et al. Long-term postoperative cognitive dysfunction in the elderly: ISPOCD1 study. Lancet 1998; 351: 857–61.[Web of Science][Medline]
- Johnson T, Monk T, Rasmussen LS, et al. Postoperative cognitive dysfunction in middle-aged patients. Anesthesiology 2002; 96: 1351–7.[Web of Science][Medline]
- Culley DJ, Yukhananov RY, Baxter MG, Crosby G. Memory effects of general anesthesia persist for weeks in young and aged rats. Anesth Analg 2003: 96: 1004–9.[Abstract/Free Full Text]
- Culley DJ, Yukhananov RY, Baxter MG, Crosby G. Sustained impairment of novel learning following isoflurane-nitrous oxide anesthesia in young and aged rats. Presented at the Annual Meeting of the American Society of Anesthesiologists, Orlando, FL, October 12–16, 2002:A-39.
Response
John Butterworth, MD, and
John W. Hammon, MD
Departments of Anesthesiology and Cardiothoracic Surgery, Wake Forest University School of Medicine, Winston-Salem, NC
In Response:
We thank Drs. Culley and Crosby for their kind letter. We agree that many patients have brief periods of cognitive impairment after surgery and general anesthesia, and that these brief episodes are probably unrelated to microemboli, particularly in patients not having cardiac, neurological, or orthopedic surgery. Even in cardiac surgery, neurobehavioral deficits observed within the first postoperative days do not have the same prognostic significance as similar deficits observed 6 wk or later after surgery. This was why the Statement of Consensus on Assessment of Neurobehavioral Outcomes after Cardiac Surgery (1995) recommended outcome assessment no sooner than 3 mo (1).
When testing is appropriately delayed after cardiac surgery, we believe that it is a reasonable assumption that the strokes and neurobehavioral deficits then identified result from similar brain injury mechanisms.
Reference
- Murkin JM, Newman SP, Stump DA, Blumenthal JA. Statement of consensus on assessment of neurobehavioral outcomes after cardiac surgery. Ann Thorac Surg 1995; 59: 1289–95.[Free Full Text]
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